Dispensers for delivering a beneficial agent to the environment of use are known to the prior art. For examle, one dispenser is disclosed in U.S. Pat. No. 3,995,632 issued to Nakano, Higuchi and Hussain. This patent discloses a dispenser comprising a saturated solution of magnesium sulfate that pushes against a melted composition. The melted composition is squeezed through a passageway from the dispenser. In U.S. Pat. No. 4,251,506 issued to patentee Laby, a device is disclosed consisting of a controlled release composition for administration of a therapeutic agent to a ruminant. The patent discloses in detail a spring for pushing a composition from the dispenser. The use of a spring as a driving force limits the practical use of the device as the driving force of a spring diminished by the distance through which the spring operates. For this device drug delivery decreases over time as the spring elongates and concurrently weakens. The delivery rate is influenced also by the nature of the composition and its interaction with fluid at the interfaced environment of use. The interface provides exterior mechanical action that controls drug release by the environment and not by the device. Another dispenser is disclosed in U.S. Pat. No. 4,327,725 by inventors Cortese and Theeuwes. The dispenser disclosed in this patent comprises a hydrogel that urges an aqueous formulation through a passageway from the dispenser. In U.S. Pat. No. 4,350,271 issued to Eckenhoff, a dispenser is disclosed comprising a water swellable composition that pushes a lipophilic fluid from the dispenser. U.S. Pat. No. 4,612,008 issued to Wong, Barclay, Deters and Theeuwes discloses a dispenser wherein an expanding polymer urges a drug formulation comprising an aqueous osmotically active solution from the dispenser. Another dispenser is disclosed by patentees Eckenhoff, Cortese and Landrau in U.S. Pat. No. 4,595,583. The dispenser disclosed in this patent comprises an expandable aqueous activated osmopolymer that urges a heat responsive composition through an orifice from the dispenser.
The dispenser of the prior art presented above represents an outstanding and pioneering advancement in the dispensing art, and they are additionally useful for dispensing innumerable beneficial agents to an environment of use. Now, this present invention has unexpectedly discovered that a dispenser can be made available comprising a novel and unobvious dispensing means unknown heretofore the delivery a beneficial agent to an environment of use. That is, it has now been discovered that a dispenser can be provided comprising means for delivering a bio-affecting beneficial agent in a substantially formulated solid form at a kinetically controlled rate substantially equal to its kinetic rate of release from the dispenser. The dispenser thereby makes available to a beneficial agent receptor controlled and constant prolonged delivery of a beneficial agent according to a preselected built-in optimal program of beneficial agent presentation.